The exemplary embodiments of this invention relate generally to semiconductor devices and methods for the fabrication thereof and, more specifically, to methods of using thin film stress layers in conjunction with epitaxial lift off techniques to accelerate etching processes in the formation of semiconductor devices.
Optoelectronic devices such as solar cells generally incorporate multiple semiconductor device layers. Such device layers are typically flexible to some degree and are fabricated by being grown or otherwise formed on and subsequently separated from parent substrates of semiconductor material (e.g., III-V materials such as gallium arsenide (GaAs)). The semiconductor device layers may be separated from the parent substrates using epitaxial lift off (ELO) techniques. The ELO techniques generally involve the use of a sacrificial release layer under the semiconductor device layer, with the sacrificial layer being etched with hydrofluoric acid (HF) to release the semiconductor device layer from the parent substrate. However, such processes using HF etching of sacrificial layers are oftentimes very slow.
Other ELO techniques utilize wax stressor layers on the semiconductor device layers to assist with the epitaxial lift off of the semiconductor device layers from the parent substrate. Still other techniques involve mounting foils with wax on the semiconductor device layers and carrying out the epitaxial lift off by loading the mounting foils using weight in conjunction with etching the sacrificial release layer using HF.